In modern communication systems, communication connections (for example, communication connections for the transmission of speech, video or multimedia information) are increasingly transmitted via packet-oriented communication networks, such as local area networks (LAN) or wide area networks (WAN). For example, internet telephony commonly referred to as VoIP (voice/video over internet protocol) is based on this technology.
An important feature of a communication connection is its service quality. The service quality of a communication connection is frequently also referred to as quality of service (QOS) and can refer to various transmission or connection properties, such as the transmission bandwidth, the transmission error rate, a transmission delay or other transmission or service quality resources.
To ensure a prescribed service quality, devices called resource managers are frequently deployed. A resource manager is included in a communication network or a part of a network and administers the network's transmission or service quality resources. Through the resource manager, prescribed transmission resources and service quality resources, which are usually structured into service quality classes or traffic classes, can be reserved for a particular connection. For reserving a transmission or service quality resource, a service quality request is transmitted to the resource manager by an end device. The resource manager then checks the availability of the requested transmission or service quality resource and, depending on the availability, either permits the requested connection or rejects it.
Once the connection has been permitted, the end device can transmit a communication data flow of the assigned service quality class to the network access device of the communication network. The network access device assigns the communication data flow to the requested service quality class and transmits it in the service quality class through the communication network.
Because a communication network also frequently transmits connections from network-external end devices or communication applications, the arrival at the end device of a communication data flow from a transmission that has not been approved by the resource manager cannot, in general, be excluded. In order to prevent such a communication data flow from having a service quality that was elsewhere assigned to it, and therefore illegitimately using bandwidth, the currently used known methods ensure the service quality by carrying out an analysis of the signaling protocol by the network access device.
Such a protocol analysis, however, requires status-dependent and context-dependent administration of all the data packets arriving that are associated with connections. This administration is both costly and susceptible to errors. A less costly and less error-prone method is sought for ensuring desired service quality for communication data flows in a communications network.